Impact tool



May 20, 1924. v 1

s. l. PRESCOTT IMPACT TOOL Filed Jan. 12; 1923' 2 Sheets-Sheet. i

IN VENTOR res PAENT FFICE.

SYDNEY I. PRESCOTT, OF NEW YORK, N. Y.

IMPACT TOOL.

Application filed January 12, 1923. Serial No. 612,162.

To all whom it may concern:

Be it known that I, SYDNEY I. Pnnsoo'rr, a citizen of the United States, residing at New York, county of New York, and State of New York, have invented a new and useful Improvement in Impact Tools, of which the following is a specification.

This invention relates to an improvement in portable impact tools, particularly to those in which power is derived from internal combustion engines or motors.

In impact tools of this type heretofore known, the pressure ofexploding gas has been used for driving the hammer, the en-. gine used being of the two-stroke-cycle type andgenerating only one effective blow per engine revolution. The speed of engines of this type is low and the blows per minute are limited by the engine speed. For certain work this hammering speed is insufiicient and one of the objects of the present invention is the production of a portable impact tool embodying a motor running at its most efficient speed, and a hammer driven thereby but operating twice as fast as the motor. Also in the devices of this type heretofore known, the engine piston was subjected to excessive shock due to its direct connection with the hammering devices, and this interfered with proper operation of the engine. It is another object of this invention to produce a portable impact tool in which the working parts of the motor are free from the shock developed by the hammer so that the motor will run smoothly at all times. .Also in the e'arlierdevices, the force of the blows delivered depended upon the force of the gas explosions, and these varied. An.- other object of the present invention is the production of a portable impact tool in which the hammer is spring driven so that blows delivered will be equal regardless of the engine speed or force of gas explosions. Also in the earlier devices, no means was provided for varying the force of the blows delivered in accordance with the character of the work to be done, although the same force of blow is not required in all cases. Another object of the invention, therefore, is the production of a portable impact tool in which provision is made for the delivery "-ofsblows' of varying force by simple substitution of hammer driving springs of difierent power selected in accordance with the J -particular work to-be done. And also in .the earlier devices, the engine used was not useful for any other purpose because it was so inbuilt with the hammer mechanism that the two could not be disconnected. It is another object of this invention to produce a portable impact tool which, whennot used for impact tool purposes, may be used for other purposes, such as driving a churn, grindstone, feed-cutter, pump, and similar implements. With these and other objects not specifically mentioned in view, the invention consists in certain constructions and combinations which will be hereinafter-fully described and then specifically set forth in the claims hereunto appended.

In the accompanying drawings, which form a part of this specification and in which like characters of reference indicate the same or like parts, Fig. 1 is an elevation, partly broken away, of a device constructed in accordance with the invention; Fig. 2 is, a sectional elevation of the structure shown in Fig. 1, the plane of the section lying at right angles to that in Fig. 1; "Fig. 3 is a sectional elevation taken on the line 33 in Fig. 1; and Fig. 4 is a perspective view of a device for holding the hammer out of action.

In carrying the invention into eifect there is provided a hammer, a power-spring driving said hammer, means for stressing and releasing said power-spring, and a motor driving said means, so that the whole unit is self-contained and independent of a separate power plant. In the best constructions, the stressing and. releasing means is a component part of the motor and the latter is in the form of an internal combustion engine; the stressing and releasing means comprises a cam operating to stress and release the power-spring through the agency of the hammer itself; the stressing and releasing means is adapted to act twice during each motor revolution, in order to produce high impact speed from relatively .low motor speed; and a buffer-spring acts on the hammerto limit its throw beyond its normal point of impact in order to avoid subjecting the'device to excessive shock when a steel i creases, an

Referring to the drawin there is provided a hammer which, as s own, comprises a head 4, a shank 5, a laterally extending toe 6, a rectangular heel 7, and a tail 8 extending upwardly from the toe. The hammer is adapted to reciprocate, and rotation is prevented by the engagement of the heel 7 with a slideway 9 formed on the interior of a two-part housin 10-11, which housing is the crankcase 0 an internal combustion engine provided to control the reciprocationof thehammer. |The two parts of the crankcase are held together in the customary manner by means of, bolts 12, 13 and 14.

The lower part 11 of the crankcase is provided with a depending cylinder 15 in which the "hammer head 4 reciprocates. The crankcase forms an oil reservoir and to prevent the escape of oil through the cylinder 15 past the hammer head 4, the latter is provided with oil retaining means consisting, in the device selected to illustrate the invention, of piston rings 16. The lower part of the crankcase has a further extension below and in axial alignment with the cylinder 15, which forms a chuck 17 having a hexagonal bore adapted toreceive the hexagonal shank of a steel 18, the upper end of which normally rests against the lower surface of the hammerhead 4.

When the device is in operation the hammer is given a reciprocating movement; that is, it is retracted out of contact with the upper end of the steel 18, and then driven down into contact with the same. For the purpose of driving the hammer, there is provided a power-spring 19, coiled around the tail 8 of the hammer, the lower end of the spring bearing against the toe 6 before referred to, and the upper end bearing against the top of the upper section 10 of the crankcase. When the parts are in the position shown in Fig. 2, the power-spring 19 is onl slightly compressed and has little power. ut as it is compressed by mechanism to be (presently described, its power inwhen the hammer is released by the same means which compresses the spring, this .power instantly drives the hammer It will be understood that since the force ofv the blow depends upon the same compression of the same spring in every instance, the blows will be of uniform force regardless of their rapidity.

The tail 8 of the hammer projects upwardlmthrough an aperture 20 in the top of the upper section 10 of the crankcase, and

the hammer above the aperture 20 and outside the crankcase. The lower end of this spring bears against the top of the upper section 10 of the crankcase, and its upper end is normally a little out of contact with the nut 22 threaded on to the upper end of the tail 8, as clearly shown in Fig. 2. It will be understood that when the power-spring 19 is compressed, the clearance between the buffer-spring 21 and the nut 22 increases. lVhen the hammer drops, however, impact is made about one-sixteenth of an inch before the nut 22 will engage the upper end of the buffer-spring 21, provided the steel 18 is in its proper position. Since all of the work is done by impact, from that point on the buffer-spring acts to slow down and stop leasing the power-spring 19 is a componentv part of a two-cylinder two-stroke-cycle internal combustion engine having a crankshaft provided with two cranks 23-24, and a double bifurcated cam 25- 25 lying between said cranks, the .bifurcations of the cams straddling the .shank of the'hammer and en%aging the under side of the toe 6 at 26. seen that the cams 25 each have a curved operating surface 27 and an abrupt radial drop 28. The crankshaft ismounted in ball bearings 29-of the usual construction and supported in split bosses 30 extending laterally from. the crankcase 10, 11 before referred to. Upon one end of this crankshaft is secured a flywheel 31 and upon the opposite end is secured a starting disk 32-provided with a notch 33 adapted for engagement 1 with a starting crank not shown. Packing rings 34 and 35 of well known construction are provided for keeping the oil in the cranky an inspection of Fig. 2, it will be a case out of the bearings and for keeping clean lubricant in the bearings. v

The crankshaft is rotated by means of connecting rods 36-37, the lower ends of which are respectively journaled on the cranks 23 and 24, The upper ends of the connecting rods 36 and 37 terminate in wrist pins 38, b0th being alike. Each of these wrist pins is journaled in a cross head 39 and is held in place therein by means of a washer 40 and pin 41. 39 reciprocates in oppositely disposed slideways 42-42 machined in thenpper section as shown, is integral with a piston rod 43 ing-box 44 at the top of the upper section 10 of the crankcase, the stufiing-box acting Each cross head a and each piston rod works through a stufi- ,125 10 of the crankcase. Each cross head 39,

2 cylinder is provided with the usual spark ertures 56 in the upper section 10 of the as a pilot to insure accurate alignment of engine cylinders 45 with the upper section 10 of the crankcase. The upper end of each piston rod 43 is secured to a piston 46 by means of a nut 47 and dowel pin 48. Each cylinder is provided withan intake port 49 leading from a carburizing device, of well known construction and not shown, to a bypass 50 in open communication with an induction chamber 51 below the piston 46, and above the stuflin --box 44, and in intermittent communicati n through a port 52 with the combustion chamber 53 of the cylinder. Each cylinder also is provided with a pair of exhaust ports 54 discharging into a'short exhaust pipe 55.

It will of course be understoodthat each plug and other ignition mechanism includ mg a timing device projecting -through apcrank chamber, the timing devices being operated by timing cams 57--57 "formed on the crankshaft before referred to.

The power-spring 19 is readily replaceable by others of different power in order that the force of the blows delivered may be widely varied within the spring compressing capacity of the engine, when the character of the work to be done makes it desirable, without requiring anychange in the engine or in the hammer.'

When desired, the hammer may be fully retracted by means of the cam 25, and then a bifurcated block 58 may be inserted between the upper end of the buiferspring 21 and the nut 22. This will hold the hammer out of action, and the engine may then be used for other purposes, such as driving a churn, grindstone, feed-cutter, pump, or similar implements.

'When the parts are in the position shown in the drawings, the piston connected with the crank 23 is in its uppermost positiou and a charge of gas behind it has Just been jfired. The piston therefore starts downwardly on its power stroke and begins to lift the toe 6 of the hammer through the a ency of the curved surfaces 27 of one of the cams 25. the other one being idle at this time. As the piston moves downward, the crank 23 follows its orbital path and increases its turning effect as an increase of power is required to further lift the toe 6 and further compress the power-spring 19. When the crank 23 has reached a position 90 degrees from its uppermost position,

I that is, at half stroke, the toe 6 of the ham mer rides off the. curved surface 27 of the cam 25 and is free to move downwardly along the abrupt drop 28- of the cam. It will be noted that this drop is much longer than the lift from normal position, as shown, to releasing position; this is provided for the overthrow of the hammer be- .ing internal combustion engine, a

yond its normal point of impact. As the crank 23 moves downwardly beyond half stroke, it acts to store energ in the flywheel and to compress the c arge in the other cylinder where the piston is atthat time moving upward, both cams being idle during the second half of each power stroke.

By the construction above described, two explosions occur during each engine revolutron and two blows are struck a steel in the chuck 17 during the same interval. In this manner, high hammering speed is obtained from low engine speed; no moving part of the engine is subjected to hammer shock and consequently the engine runs smoothly; the blows struck are of e ual force regardless of the speed of the engine;

the force of the blows may be regulated in accordance with the character of the .work.

to be done; and the engine may be operated independent of the hammer, in the interest of convenience and economy.

What isclaimed is:

1. An impact tool comprising a reciprocating internal combustion englne, a hamspring coiled around said hammer and act ing to limit its throw pact position.

beyond its normal im 4. An impact tool comprising a reciprocating internal combustion engine, a ham;

mer, and interposed means for producing a plurality of hammer impacts during each cycle of engine operation. and a housing havin a slidewa'y for said hammer.

5. n impact tool comprlsmg a recipro; cating internal combustion engine, a ham mer, and interposed means for producing a plurality of hammer impacts durin each cycle of engine operation, and means for holding said hammer'out of action to permit independent use of said engine. 6. An impact tool comprising a reciprocathammer, and interposed means for producing a plurality of hammer impacts during each cycle of engine operation, said hammer having a head operating in an oil-tight cylmder,

7.,An impact tool comprising a reciprocating internal combustion engine, a hammer, and interposed means for producing a cating internal combustion engine, a

plurality of hammer impacts during each cycle of engine operation, said hammer being engaged by said means during retraction. 8. An impact tool comprising a reciprocating internal combustion engine, a hamner, and interposed means for producing a plurality of hammer impacts during each cycle of engine operation, said hammer being free from said means during impact.

9. An impact tool comprising a reciprocating internal combustion engine, a hammer, and interposed means for producing a plurality of hammer impacts during each cycle of engine operation, said hammer having an ofit'set toe engaged by said means during retraction.

10. An impact tool comprising a reciprohammer, and interposed means for producing a plurality of hammerimpacts during each cycle of engine operation, said means including a double-acting cam engaging said hammer.

11. An impact tool comprising a reciprocating internal combustion engine, a hammer, and interposed means for producing a plurality of hammer impacts during each cycle of engine operation, said means includ ing a double-acting cam engaging said hammer and rotating at engine speed.

12. An impact tool comprising a reciprocating internal combustion engine, a hammer, andinterposed means for producing a plurality of hammer impacts during each cycle of engine operation, said means including a power-spring actuating said hammer.

13. An impact tool comprising a reciprocating internal combustion engine, a hammer, and interposed means for producing a plurality of hammer impacts during each cycle of engine operation, said means lncluding a helical ower-spring coiled around and actuating sai hammer.

14. An impact tool comprising a reciprocating internal combustion engine, a hammer, and interposed means for roducing a plurality of hammer impacts uring each c cle of engine operation, said means inc uding a power-spring actuating said hammer and'interchangeabl e with others of different power to permit hammer impacts of different force by interchange of springs.

15. An im act tool comprising a reciprocating interna combustion engine, a hammer,

and inter osed means for roducing a plurality of ammer impacts uring each cycle of engine operation, one part of said means being operative at, engine speed and the other part at hammer speed.

16. Animpact tool comprising a reciprcating internal combustion engine, a hammer, and interposed means for producing a plurality of hammer impacts during each cycle of engine operation, said engine having a rotating element associated with said means.

17. An impact tool comprising areciprocating internal combustion engine, a hammer, and interposed means for producing a plurality of hammer impacts during each cycle of engine operation, said engine having a crankcase forming an oil-tight housing for said hammer and said means.

18. An impact tool comprising a recipro' cating internal combustion engine, a hammer, and interposed means for producing a plurality of hammer impacts during each cycle,

cycle of engine operation, said engine acting through said means twice during'each engine revolution.

21. An impact tool comprising a reciprocating internal combustion engine, a'hammer, and interposed means for roducing a pluralit of hammer impacts uring each cycle 0 engine operation, said engine acting through said means twice durlng each engine revolution, said hammer being reciprocable in the crankcase of said engine, and said means including a double-acting camon the crankshaft of said en ine and engaging said hammer and also mcluding a power-spring actuating said hammer.

In testimony whereof, I have signed my name to this specification.

. YDNEY I. PRESCOTT. 

